This invention relates to electric switches, and particularly to multiple push-button switches having three operating modes or conditions for controlling a plurality of circuits such as those of a motor vehicle lighting system.
Control switches for vehicle lighting systems have three typical operating conditions: one in which no contacts are closed, a second in which one set of contacts are closed to energize the vehicle parking light and tail light circuits, and a third position in which two sets of contacts are closed to energize the vehicle headlight circuit as well as the parking light and tail light circuits. One type of vehicle lighting control switch which has found wide use in the past employed a single longitudinally reciprocating actuator or operating member manually movable between three operating positions. Other vehicle lighting control switch constructions have been devised which include a pair of interacting operating members movable between two operating positions. This type of multiple switch has been disclosed, for example, in U.S. Pat. Nos. 3,504,372, 3,706,866, 4,213,017 and 4,323,744.
Since a vehicle lighting system typically has three operating modes, it would be desirable to employ a push-button switch having three selectively operable push-button actuators, one for each operating mode. Multiple push-button switches of this general type are known in the prior art and are disclosed, for example, in U.S. Pat. Nos. 2,790,858 and 4,143,252. The prior art switches of this type would be generally somewhat bulky, complicated and expensive when adapted for reliable operation of a motor vehicle lighting system and especially so when provided with means for illuminating the push-button actuators.
Another multiple push-button switch of substantially less cost and complexity is described in U.S. Pat. No. 2,469,650. The switch construction shown in this patent does, however, have some shortcomings. In particular, contact opening and closing takes place directly between the spring contact fingers and the locking bars and therefore would be unsuitable for switching the substantial load currents of vehicle lighting system. Accordingly, this switch would not be capable of reliable operation as a vehicle lighting control switch.
As shown by U.S. Pat. Nos. 2,458,807 and 3,873,955, there are other constructions of push-button switches known in the prior art that employ a latch member to releasibly latch a resilient contact contact carrying arm or strip in an actuated position to which it has been deflected by depression of a push-button actuator. The latch member is generally disengaged from the resilient arm or strip by a thermally responsive bimetallic element, although in some constructions of this type it may also be unlatched by returning the push-button actuator to its extended position. Such arrangements clearly are not suited for use in multiple push-button switches wherein various switch operating modes are selected by mere depression of the push-button actuators.